The notion of Ubiquitous (or Pervasive) Computing was first eloquently described by Mark Weiser at Xerox PARC in the early 1990's. He proposed a vision in which the personal computing model would evolve from one person using one computer, to many (perhaps hundreds) of computers per person; and that computing would become wirelessly embedded in the world around us, tacitly supporting our work practice. Today, twenty years later, we find ourselves surrounded by smartphones, tablets, and digital televisions much like the components of his vision: Tabs, Pads and LiveBoards. This talk will look back on what was envisioned, compare it with the reality of todays mobile market, examining what was correctly predicted, what worked and what did not. And then, reviewing key market trends, we will look forward to consider the future opportunities for pervasive computing, and some of the challenges and important use cases that we now need to consider.

In this paper, we investigate the problem of channel bounding in wireless local area networks (WLANs). We propose a MAC protection mechanism to combat the hidden node problem on non-primary channels of a basic service set (BSS). Simulation results show that the proposed MAC protection mechanism is effective in combating hidden nodes and improving throughput of 80MHz stations. The proposed scheme has been adopted into the IEEE 802.11ac specification as a mandatory feature. Furthermore, we extend the medium access mechanisms defined in 802.11n for a wider bandwidth, evaluate fairness of the 802.11n PIFS medium access mechanisms, and compare the performance of a dynamic bandwidth scheme with that of a static bandwidth implementation.

In this paper, we investigate the problem of multi-user spatial division multiple access (MU SDMA) operation in mmWave wireless networks, within which directional antennas are used to combat the high path loss incurred in the 60GHz band. We study the feasibility of MU SDMA in mmWave networks and propose two MAC protocols to support CSMA/CA based uplink and downlink MU SDMA transmissions. The proposed protocols adopt virtual carrier sensing and allows multiple users to communicate with an access point (AP) simultaneously. Performance analysis and simulation results both show that the proposed protocols can achieve considerable performance improvements over a system that supports only single user (SU) operation.

In recent years, the millimeter wave (mmWave) technology has gained considerable interest due to the huge unlicensed bandwidth (i.e., up to 7GHz) available in the 60GHz band in most part of world. In this paper, we investigate the problem of medium access control (MAC) in mmWave wireless networks, within which directional antennas are used to combat the high path loss incurred in the 60GHz band. We extend a directional CSMA/CA protocol presented in our prior work by exploiting spatial reuse. The proposed protocol adopts virtual carrier sensing and allows non-interfering links to communicate simultaneously. We present a performance analysis as well as simulations to evaluate the proposed protocol. Our results show that the directional MAC with spatial reuse can achieve considerable performance improvements over the 802.11 MAC and the protocol proposed in our prior work. It introduces low protocol overhead and has robust performance even when the network is heavily congested.

Multiple-input multiple-output (MIMO) is one form of the smart antenna technology that uses multiple antennas at both the transmitter and receiver to improve communication performance. In this paper, we investigate the problem of medium access control in wireless local area networks (WLANs) with downlink multi-user MIMO (DL MU MIMO) capability. We propose a CSMA/CA MAC protocol with three response mechanisms for DL MU MIMO and compare the performance of DL MU MIMO with the beam-forming (BF) based approach. A novel per-station weighted queuing mechanism is proposed to mitigate the hidden node problem in the network. Performance analysis and simulation study both show that the proposed DL MU MIMO mechanism incurs low overhead and provides significant throughput performance gain over BF based approach in high SNR scenarios.

Collaborative spaces supporting personal mobile devices provide for a powerful integration of personalized content with supportive embedded infrastructure. Social, spatial, and informational considerations have a salient impact on such modern collaborative spaces. The design, implementation, and evaluation of a collaborative workspace prototype that directly supports the integrated use of mobile devices not only yields insights into the basic capabilities behind such a space, but also a deeper understanding of the different composition control mechanisms available. Specifically, such environments can effectively work with existing laptop platforms, and show increased promise for supporting future generations of smaller mobile devices.

In this paper, we investigate the training problem of wireless local area networks (WLANs) with downlink multi-user multiple input multiple output (DL MU MIMO) capability. We extend the 802.11 MAC protocol and propose a few training protocols at the MAC layer to support DL MU MIMO. We provide a capacity analysis based on measurement results from an 802.11n systems, evaluate the overhead of these training protocols, and compare the performance of DL MU MIMO with that of a beam-forming (BF) based approach. Through simulation studies, we find that at high SNR and with implicit training, the DL MU MIMO mechanism provides significant performance gain over the BF based approach. Furthermore, our capacity analysis and simulation study also show that it is critical to define appropriate training intervals based on antenna configuration, channel mobility, and CSI feedback overhead.

This paper presents an architecture that affords mobile users greater trust and security when browsing the internet (e.g., when making personal/financial transactions) from public terminals at Internet Cafes or other unfamiliar locations. This is achieved by enabling web applications to split their client-side pages across a pair of browsers: one untrusted browser running on a public PC and one trusted browser running on the user's personal mobile device, composed into a single logical interface through a local connection, wired or wireless. Information entered via the personal device's keypad cannot be read by the PC, thwarting PC-based key-loggers. Similarly, information displayed on the personal device's screen is also hidden from the PC, preserving the confidentiality and integrity of security-critical data even in the presence of screen grabbing attacks and compromised PC browsers. We present a security policy model for split-trust web applications that defends against a range of crimeware-based attacks, including those based on active-injection (e.g. inserting malicious packets into the network or spoofing user-input events). Performance results of a prototype split-trust implementation are presented, using a commercially available cell phone as a trusted personal device.

Phenomenal growth in the performance and functionality of portable electronic devices has transformed our notion of mobile computing from its roots in the early 90's. In fact, some of the advances are so remarkable that 20 years ago they would have seemed improbable; the exponential growth in the density of solid-state storage being a prime example. Looking forward, can we expect a similar leap in mobile capabilities over the next 20 years? In this presentation, I will examine the trends in processing, storage, wireless networking, displays, data-entry, sensing and battery design, trying to predict the properties of future mobile computers. In order to better understand how the evolution of mobile technology will progress, I will also consider how our lives, needs and work practices might shape the design of these systems, and provide us with powerful tools that are not only functional, but enable a richer user experience.

The Musicology project examines the user, ecosystem, and technology aspects necessary to enable playback of personal music in public spaces. User surveys, field interviews, and a technology prototype inform a discussion relating to privacy and identity, content control, and power consumption (among others). Understanding how mobile devices can be used to present personal content, initially with audio but eventually through photographs and other media, has the potential to open up new avenues for personal expression, bringing the motivations behind online content sharing websites into a publicly social arena.

The Gesture Connect system streamlines the process of connecting to and/or controlling objects from a user's personal mobile device. Typically, in order to connect two devices together they users must follow a two-step process that consists of first selecting which devices should be connected, and then specifying what the devices should do once they are connected. By combining contact-based connections with gesture-based selection, the Gesture Connect system combines these two steps into a single physical action for simple actions, greatly simplifying the common case. In order to demonstrate and test the underlying concept, a hardware extension comprising Near Field Communication (NFC) and accelerometer capability has been developed for standard commercial mobile phone devices, along with the associated tagging and gesture recognition software. This system greatly reduces overall interaction time for common-case interaction, enhancing the overall user experience.

CoolSpots enable a wireless mobile device to automatically switch between multiple radio interfaces, such as WiFi and Bluetooth, in order to increase battery lifetime. The main contribution of this work is an exploration of the policies that enable a system to switch among these interfaces, each with diverse radio characteristics and different ranges, in order to save power - supported by detailed quantitative measurements. The system and policies do not require any changes to the mobile applications themselves, and changes required to existing infrastructure are minimal. Results are reported for a suite of commonly used applications, such as file transfer, web browsing, and streaming media, across a range of operating conditions. Experimental validation of the CoolSpot system on a mobile research platform shows substantial energy savings: more than a 50% reduction in energy consumption of the wireless subsystem is possible, with an associated increase in the effective battery lifetime.

The terms Ubiquitous and Pervasive computing were first coined at the beginning of the 90's, by Xerox PARC and IBM respectively, and capture the realization that the computing focus was going to change from the PC to a more distributed, mobile and embedded form of computing. Furthermore, it was predicted by some researchers that the true value of embedded computing would come from the orchestration of the various computational components into a much richer and adaptable system than had previously been possible. Now some fifteen years later, we have made progress towards these aims. The Hardware platforms used to implement these systems encapsulate significant computation capability in a small form-factor, consume little power and have a small cost. However, the system software capabilities have not advanced at a pace that can take full advantage of this infrastructure. This paper will describe where software and hardware have combined to enable ubiquitous computing, where these systems have limitations and where the biggest challenges still remain.

Advanced personal wireless mobile devices, such as today's emerging smart phones, are capable computers that have the potential to enable individuals to share personal content, such as photographs, music, and video. Face to face sharing can be a satisfying and even emotional experience, yet it is not well supported by existing digital technologies, which typically isolate media into separate collections or require that they be manually combined into a single collection on a single machine. Federating wireless mobile devices with fixed infrastructure, such as a digital home entertainment center, provides a lightweight, unified, and intuitive way to share media among friends and family. This paper looks at both technological and social issues that surround sharing media using federated devices, considering the relevant emerging technologies, media types, and usage contexts.

A detailed power analysis of a multi-radio mobile platform highlights the complex tradeoffs between the computation, storage, and communication subsystems. The particular mobile device, which does not include an LCD or other on-board display, can be used as a source for audio or video media files, or a source/sink for secure data transfers. A version of the device has been augmented with fine-grained power monitoring capability and used to obtain detailed measurements of power dissipation in the various subsystems. Analysis of these measurements sheds light on the power consumption characteristics of different applications, thereby providing hints to system designers about potential areas for optimization. Specifically, this work contrasts the power efficiency of the various wireless technologies supported by the system.

Storage capacity and communication bandwidth are two factors that significantly impact the design and implementation of mobile systems. Furthermore, storage density is increasing at an exponential rate faster than the associated communication bandwidth. High-density storage in very small form factors will enable new classes of applications that would not be possible in systems which rely heavily on communication. These applications, which involve continuous capture, pre-loaded content, and proactive data loading, will help overcome some of the barriers presented to mobile systems. Researchers would be prudent to recognize these trends and better understand how technology growth will impact their research agenda.

TiltType is a novel text entry technique for mobile devices. To enter a character, the user tilts the device and presses one or more buttons. The character chosen depends on the button pressed, the direction of tilt, and the angle of tilt. TiltType consumes minimal power and requires little board space, making it appropriate for wristwatch-sized devices. But because controlled tilting of one's forearm is fatiguing, a wristwatch using this technique must be easily removable from its wriststrap. Applications include two-way paging, text entry for watch computers, web browsing, numeric entry for calculator watches, and existing applications for PDAs.

The role of computers in the modern office has divided our activities between virtual interactions in the realm of the computer and physical interactions with real objects within the traditional office infrastructure. This paper extends previous work that has attempted to bridge this gap, to connect physical objects with virtual representations or computational functionality, via various types of tags. We discuss a variety of scenarios we have implemented using a novel combination of inexpensive, unobtrusive and easy to use RFID tags, tag readers, portable computers and wireless networking. This novel combination demonstrates the utility of invisibly, seamlessly and portably linking physical objects to networked electronic services and actions that are naturally associated with their form.

This paper describes a novel physical icon [3] (“phicon”) based system that can be programmed to issue a range of commands about what the user wishes to do with handdrawn whiteboard content. Through the phicon's UI, a command to process whiteboard context is issued using infrared signaling in combination with image processing and a ceiling-mounted camera system. We leverage camera systems that are already used for capturing whiteboard content [4] by further augmenting these systems to detect the presence and location of IR beacons within an image. An HDLC-based protocol and a built-in IR transmitter are used to send these signals.

This paper reports on the design and use of tactile user interfaces embedded within or wrapped around the devices that they control. We discuss three different interaction prototypes that we built These interfaces were embedded onto two handheld devices of dramatically different form factors. We describe the design and implementation challenges, and user feedback and reactions to these prototypes. Implications for future design in the area of manipulative or haptic user interfaces are highlighted.

In this paper, we describe the process behind the design of Audio Aura. The goal of Audio Aura is to provide serendipitous information, via background auditory cues, that is tied to people's physical actions in the workplace. We used scenarios to explore issues in serendipitous information such as privacy and work practice. Our sound design was guided by a number of strategies for creating peripheral sounds grouped in cohesive ecologies. Faced with an physical and software infrastructure under development in a laboratory distant from our sound studio, we prototyped different sonic landscapes in VRML worlds. In our infrastructure design, we made a number of trade-offs in our use of legacy systems and our client-server design. Keywords: Audio, Augmented Reality, Auditory Icons, Active Badge, VRML. Earcons, Awareness, Periphery INTRODUCTION In this work we explore using audio to connect a person's activities in the physical world with information culled from the virtual ...

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A novel system for the location of people in an office environment is described. Members of staff wear badges that transmit signals providing information about their location to a centralized location service, through a network of sensors. The paper also examines alternative location techniques, system design issues and applications, particularly relating to telephone call routing. Location systems raise concerns about the privacy of an individual and these issues are also addressed.